The invention concerns a drive arrangement of a motor vehicle.
Drive arrangements of this type are also in use in large numbers in commercial vehicles. To shift gears, the driver usually opens the disconnection-type clutch or starting clutch manually by activating the clutch pedal. After the new gear is set by activation of the shift lever, the clutch is closed again. Slippage on the clutch usually arises for a short time while closing the clutch.
Whether a gear shift is felt to be comfortable and how great the clutch wear and tear is depends basically upon what motor load or motor rotational speed is applied by the driver on the accelerator pedal during the closing of the clutch. Inexperienced drivers frequently cause unintended shifting shocks and/or a high clutch wear and tear when re-engaging the clutch.
The invention is, therefore, based upon the objective of supporting the driver of a motor vehicle with a manual gear shift so that comfortable gear shifts with little clutch wear and tear are reliably achieved.
In contrast with a drive arrangement with a conventional, manual gear shift, the drive arrangement of the invention has a clutch status recognition apparatus, an apparatus for determining the rotational speed of the shifting gearbox, and a control device that receives signals from the clutch status recognition apparatus and from the rotational speed determination apparatus. The control facility evaluates a signal from a load cell (accelerator pedal). During normal driving operation, apart from shifts, this signal is decisive for controlling motor load.
This arrangement, also designated as xe2x80x9cE-gas,xe2x80x9d is used in many modern drive arrangements.
The clutch status recognition apparatus can, for example, consist of a circuit which is arranged on the clutch pedal or on the clutch itself and shifts depending upon the activation path of the clutch. A rotational speed sensor on the gearbox input shaft serves as a rotational speed determination apparatus. The control unit is an electronic motor and/or gearbox control unit.
As soon as the disconnection-type clutch or starting clutch is opened for the purpose of shifting gears, the drive motor no longer reacts to the load specification of the driver on the accelerator pedal. Rather, in this state, the control unit adjusts the rotational speed of the output shaft of the drive motor to a desired rotational speed, which is dependent upon the rotational speed of the input shaft of the shifting gear. As soon as the disconnection-type clutch is closed again, the drive motor is again controlled by the driver by way of the accelerator pedal.
For the least clutch wear and tear, the desired rotational speed for the rotational speed of the output shaft of the drive motor is set equal to the rotational speed of the input shaft so that, upon engagement, practically no slippage prevails on the clutch.
In an advantageous embodiment of the invention is provided a recognition apparatus for a load direction before the gear change, which differentiates between the load directions xe2x80x9cpullxe2x80x9d and xe2x80x9cpush.xe2x80x9d The latter can, for example, consist of an electronic motor and/or gearbox control unit in which a pull-push characteristic curve is deposited in a memory region in the form of motor load values over motor rotational speed values.
If closing takes place toward the xe2x80x9cpullxe2x80x9d load direction, the desired rotational speed for the rotational speed of the output shaft of the drive motor is one offset amount higher than the rotational speed of the input shaft of the shift gearbox. If closing takes place in the xe2x80x9cpushxe2x80x9d direction, the desired rotational speed for the rotational speed of the output shaft of the drive motor is one offset amount less than the rotational speed of the input shaft of the shift gearbox. In this way, transmitting a torque is achieved already during the slippage phase while re-engaging the drive motor, while the load direction corresponds to the load direction before the gear shift. The phase of tractive force interruption is hereby shortened, and it is moreover ensured that no change in load direction occurs during the gear change, which would be felt to be uncomfortable. The value of the offset amount is selected so that no harmful clutch wear and tear occurs.
In an advantageous embodiment of the invention is ascertained the offset amount dependent from a tractive force level of the vehicle ahead of the gear change, wherein to a higher tractive force level is allocated a larger offset amount. With shifts in the region of the pull-push characteristic curve are thus selected only very low values for the offset amounts, so that no unintended change in acceleration results when re-engaging.
The length of time from the time point at which the new gear is set in the gearbox with an opened disconnection-type clutch up to the time point in which the disconnection-type clutch is closed is often very short. On the other hand, especially with larger drive motors, a specific period of time is needed until a desired rotational speed specification is attained. In an embodiment of the invention, a target gear predicting apparatus is hence present which predicts a target gear step on the basis of an operating status prevailing prior to the gear shift. A gearbox input rotational speed computation apparatus calculates the then presumably applying rotational speed of the input shaft of the shift gearbox on the basis of the predicted target gear step. For this calculation, a value of the traveling speed or the rotational speed of the output shaft of the gearbox as well as the gear ratio values of the individual gear steps deposited in a memory region of the electronic gearbox control unit are moreover adduced.
As long as the new gear step is not yet set, the desired rotational speed for the output shaft of the drive motor is determined in dependence upon this calculated rotational speed of the input shaft. In this way, the rotational speed of the drive motor is already influenced at an earlier point in time-namely, as a rule as soon as the clutch is opened-so that after the gear step is actually set, the rotational speed of the drive motor already largely corresponds to the then established desired rotational speed specification. The target gear predicting-apparatus is comprised by a calculation process deposited in the electronic motor and/or gearbox control unit. In the simplest case, an adjacent gear step is adopted as the target gear, while at high rotational speeds of the drive motor, the next higher gear step is adopted, and at lower rotational speeds of the drive motor, the next smaller gear step is adopted.
The invention will now be described, by way of example, with reference to the accompanying drawings in which:
FIG. 1 shows schematically a drive arrangement of the invention;
FIG. 2 represents a time progression of a pull upshift; and
FIG. 3 depicts a time progression of a pull back shift.